By Plato's 'philosophy of science' Gregory means '[his] conception of the natural world, and how we ought to investigate and explain it'. The scope of this book, though impressive, is somewhat more limited than these words would indicate. In fact, the book is principally devoted to the dialogue Timaeus, and in particular to its cosmology, astronomy, and mathematical 'chemistry'. Part of Gregory's aim is to defend Plato against critics who claim that Plato's scientific speculations are not just wrong but uninterestingly so. He argues that Plato was not in fact an enemy of empirical investigation and that he had justifiable grounds for his theoretical commitment to teleology and to mathematical reductionism. On the first score, Gregory seems entirely correct on the basis of the ample textual evidence he provides. On the second score, his defense of Plato is repeatedly qualified with the rather patronizing remark that what Plato says is interesting and impressive albeit 'within the context of 4th century B.C.E. science'. This might leave us with interesting doctrines from an historical perspective, but it will probably not do as a refutation of the claim that Plato's science holds little interest today.

The book is divided into an introduction setting out the author's fundamental position, followed by ten chapters which weave together discussions of particular doctrines in Timaeus with discussions of Gregory's understanding of the conceptual equipment Plato brings to bear on his philosophy of science. Chapter one deals with teleology generally and in Timaeus in particular. Plato's principal reasons for advocating teleology according to Gregory are that the current and ongoing order of the cosmos as well as its origin from a chaotic state cannot be explained other than by a teleological cause (26). Although the author clearly has some sympathy for Plato's teleology understood as a scientific hypothesis, and he does briefly attempt to draw some parallels with contemporary versions, he seems inclined to the view that it is a hypothesis more or less safely set aside (46-7). The second chapter is an entirely salutary demolition of the view that Plato is almost pathologically anti-empirical. Even Republic, which is most often cited in support of this view, is taken in fact to have a rather balanced view of both the desirability and limitations of observation in astronomy (62-67). As Gregory reasonably points out, it is far from clear why Plato's view of the imperfections of the sensible world should have ever been thought to entail a disregard for observation.

The third chapter is an exploration of the epistemological basis for teleology. Somewhat oddly, Gregory finds the basis in an interpretation of the Meno paradox as concerned with the paradox of the underdetermination of data in the philosophy of science. 'In the Timaeus, Plato several times faces the problem of choosing from an indefinite field of possibilities (which cosmos/what is the nature of order/the ultimate particles/celestial motion) and in each case proposes an answer which is shaped by his solution to Meno's paradox' (74). Gregory concedes that the manifest answer to Meno's paradox is the doctrine of recollection. This answer Gregory finds uninteresting (82). Instead, he suggests we go to Phaedo and Republic and the epistemological doctrines there, though it is not entirely clear how he links the 'uninteresting' answer with these. Gregory locates the 'interesting' answer to the paradox in the epistemology of Phaedo, where he argues that Socrates' 'second-best' hypothesis, the theory of Forms, is actually a theory about the minimum number of entities we must postulate to have a theory that will do all the explaining we require of it (83). Gregory is correct I think in taking Forms as explanatory entities and in assimilating teleological explanation to the postulation of a or the good, which Gregory analyzes in terms of unity, simplicity, and elegance. This is of course material that has been the subject of an immense literature and Gregory's rather hurried passage through the texts will not satisfy most. In particular, he seems to miss the opportunity to make a serious philosophical connection between Plato's teleology and contemporary intelligent design theory. This would have been a more challenging and perhaps more fruitful investigation than one which merely concludes that there is a resemblance between that teleology and a realist conception of scientific explanatory entities.

The fourth and fifth chapters are devoted to the astronomy of Timaeus. The author argues that the account of celestial motion in Timaeus, wherein that motion is held to be regular, stable, and amenable to mathematical prediction, marks an advance over a contrary account in Republic. Such a conclusion would, if sustained, lend support to the traditional late dating of Timaeus (113). Gregory distinguishes astronomical regularity based on physical law from teleological design, making the apt observation that Plato's Demiurge is not omnipotent and so must confront pre-cosmic 'necessity'. Therefore, there is conceptual space for physical law apart from the intervention of the Demiurge, though it seems that Plato wants to locate intelligibility completely on the side of the Demiurge. In that case, one would want to know wherein the intelligibility of physical law is supposed to be found, except in the way a non-realist would have it. As Gregory says, 'necessity wanders from teleology but not from regularity' (116, cf. 172 ). This sort of necessity, however, is exactly what Plato denies is possible without 'teleology'. Gregory suggests finally that Timaeus may 'share some of the optimism of Theaetetus and Philebus towards knowledge of the sensible' (123). It is not clear that by 'knowledge' Gregory means episteme. If he does, I think he is mistaken for all three dialogues. Nevertheless, his argument about Timaeus and astronomical calculation deserves to inform future discussions about Plato's later epistemology. Gregory makes the somewhat odd case that the cosmology of Timaeus should not be taken as 'literal and finished' but 'a prototype attempting to instantiate a solution to Meno's paradox' (158), where that paradox is, again, understood as the paradox of underdetermination. Plato, Gregory argues, actually recognized the defects of his model in Timaeus. He takes this position against Vlastos' view that what inspired Plato's advocacy of regular, circular ordered motion was a 'metaphysical fairy tale'. Rather, on Gregory's view, Plato was inspired by a search for 'answers to real epistemological problems of how to go about doing astronomy' (158). All of these claims are not unreasonable, though it is difficult to find in this book anything like a lucid exposition of those epistemological problems as Plato understood them.

Chapter six attempts to situate Plato's cosmology within wider traditions of Greek cosmology from the Presocratics onwards. The chapter contains an especially useful application of the distinction between regularity and law to the understanding of Greek cosmological development. There is a somewhat confusing, brief discussion of the distinction between empeiria and techne in Plato, wherein the author seems to identify the former as near to science and the latter as near to technology, though clearly for Plato (as for Aristotle), empeiria is lower on the scale than is techne. Chapters seven and eight discuss what Gregory calls Plato's 'geometrical atomism' in Timaeus, the construction of the cosmos by the Demiurge based on solid geometrical bodies. Naturally, there is here an extensive discussion of the Receptacle, its contents, and their relation to the products of the imposition of 'shapes and numbers' by the Demiurge. I find this discussion not altogether helpful, since the author does not recognize that the account of the Receptacle and its contents in Timaeus (47E4-52D2), explicitly excludes any of the contributions of the Demiurge. That is, we are being given an account of the non-intelligible aspect of sensible reality. This is so whether or not we take the creation of the cosmos literally. Accordingly, I do not see what Gregory takes as a conflict between the account of the Receptacle in Timaeus and the flux theory in Theaetetus, to which Plato is allegedly wedded. But the flux in the Receptacle does not translate into flux in the cosmos, and there is I think a good case for taking the flux theory in Theaetetus to be one that is offered only hypothetically by Plato as a necessary accompaniment to a theory that perception is knowledge. Gregory also addresses the question of whether the Receptacle can be identified in any way with matter, as Aristotle does in Physics. He argues that Aristotle questions this identification in De Caelo and in On Generation and On Corruption, even though the latter two works are generally dated close in time to the former (229-31).

Quite startlingly, after arguing extensively for Plato's serious efforts to solve real problems, chapter nine sets out to argue that Timaeus does not represent Plato's cosmological views (241). The main reason for holding this is that the assertion of definite cosmological views conflicts with Timaeus (27C-29D) wherein the ensuing study of physics is famously said to be 'a likely story' (29D2). What then is the point of the cosmology? According to Gregory, Plato is 'challenging his readers to examine their own views' (242). I find this the least satisfactory part of the book. One of the texts Gregory offers in behalf of the claim that the cosmology contradicts the principle laid down in 27C-29D is 56B4 where Timaeus is speaking about 'geometrical atomism' and claiming that it is κατὰτὸνὄρθονλόγονκαὶκατὰτὸνεἴκοτα. Gregory claims that if the account is both according to 'right reason' and according to 'that which is likely', then the former is in conflict with the strictures of 27C-29D. There are, however, at least two fairly obvious ways to take this line that do not produce the contradiction that leads to Gregory's extreme conclusion. First, we can read it (as Cornford does in his translation) as implying that in this particular instance, 'genuine reasoning' is being observed as well as 'probability'. Second, we can take the καί as epexegetic, translating the line as 'according to right reason, that is, according to what is likely' since 'the likely' is already explained as the boundary of right reason for cosmological accounts.

In addition, Gregory argues that the two-world metaphysics implicit in 27C-29D is not seriously meant by Plato and contradicted by his offering of definite cosmological views. But the two-world metaphysics is forcefully reiterated at 51E-52D and in any case, there are no grounds for holding that a likely story cannot be put in definite terms or even that a two-world metaphysics precludes anything like a scientific account of the sensible world. If, however, Plato did adhere to this two-world metaphysics, and he thought that owing to it definite accounts of the sensible world were unavailable, then it remains quite obscure what Plato would hope to gain by challenging the views of his readers. What would be the positive result of that?

Gregory seems to sign on to a version of the currently fashionable view of a 'nondogmatic' Plato (255-7). 'I take it that Plato's usual aim in writing is not so much to impart knowledge, but rather to attempt to generate understanding, and so in the main his purpose is dialectical rather than dogmatic and he attempts to create some sort of interaction between the reader and the text' (255). I think it is in fact relatively uncontroversial that Plato does not think he is imparting episteme in the dialogues, but the term 'dogmatic' here is being used rhetorically, not significantly. For it does not follow from the fact that Plato is not imparting episteme or even from the fact that he does not believe that he possesses episteme that he does not have definite views which he believes are true and whose contradictories are false. If, as Gregory holds, Plato believes he is imparting 'important cosmological principles' and views about scientific methodology (259), I fail to see why these should presumably be counted as 'dogmatic' and everything else 'nondogmatic'. The tenth chapter provides an excellent summary of the many major points made in the book, although one is left wondering how forcefully Gregory has defended the position that many of Plato's views are 'still relevant to modern debates' (274).

This is, despite its flaws, a provocative and in many ways fascinating book. It is a genuine contribution to the ongoing revision of our understanding of the history of Greek science. I do not think it is as successful in its account of Plato's epistemology or indeed of his metaphysics, if we can legitimately distinguish these from his 'empirical' science. It is well worth the attention of those especially interested in Timaeus or in ancient cosmology. Missing from the extensive bibliography is Ashbaugh's 1988 study Plato's Theory of Explanation: A Study of the Cosmological Account in the Timaeus.